poisson

  1. M

    Modeling number of days in a clinic

    Hello guys, I wish to model the number of days patients stayed in a clinic. Some of my predictors included: type of injury/disease, age, insurance, etc. Since days are count data and my data is over-dispersed, negative binomial models seem to be the appropriate technique. However, I know that...
  2. J

    Which model/function should I choose for a variable arrival-rate ?

    Now, I need to resolve a real problem. But because of lacking of statistic knowledge, I do not know how to choose a suitable statistic model/function for variable arrived-rate. My model is like the arrival model, and the arrived-rate is related with the time. In most situation, we can choose...
  3. D

    Marginal effects for poisson count data model ERROR

    Hi, just as it is stated in the title, I have a problem with creating a graph of factors influencing the number of trips abroad. Can anyone help me? I would be very grateful. This is the script I use: # MARGINAL EFFECTS FOR POISSON COUNT DATA MODEL: relative_avg <- mean(relative) work_avg...
  4. M

    Can data be classified as count data?

    Hi, I have a dataset spanning two years which consists of individuals entering some process. Once they have entered this process I want to predict the number of days they will remain in this process based on some set of covariates. There are some charateristics of the data which lead me to...
  5. B

    Probability Q help, uses combinatorics, Poisson-Distr and possibly Multinomal

    Place successively and independent of each other 20 particles into 10 boxes. Hereby, each of the 10 boxes is chosen with the same probability. a) Determine the probability of the following events 1. Exactly one particle is in box 1. 2. At least one particle is in box 1. b) Give the...
  6. S

    Approximating the probability of an event occuring from the output of a Poisson GLM

    Hi all, I have some data that includes the output of a Poisson Log Link model, that aims to predict how many times an event will occur over the period of a year. I would like to approximate the probability of at least one event occurring from this output, though I am not sure how to go about...
  7. K

    Poisson process

    Dear statisticians, I have a question that is of great importance for my master thesis in insurance science. I have obtained a dataset that records the aggregate claim size per individual in connection to health care insurance for a certain policy year. What I do not observe, however, is the...
  8. kiton

    Model fit statistic for population-average specification

    Hello everybody! For the purpose of my study I am using an exponential Poisson model with population-averaged (PA) effects, as implemented in Stata's -xtpoisson, pa- command. However, neither of the fit statics (e.g., -LogLikelihood, BIC, or AIC) are appropriate after PA estimation. Are...
  9. kiton

    (Poisson/NegBin, RE) Estimation of time-invariant predictors in a panel model

    Hello dear forum members, For a time being I had been working with the following model (Stata command format): - xtpoisson y x1 x2 x3 x4 x5, fe- where, y(it) is a count DV, x1-x2(it) are controls, and x3-x5(it) are the predictors of interest, i -- denotes an individual (N = 1750), and t...
  10. S

    Comparing mortality rates? 2-sample t-test vs Chi sq vs Poisson regression vs others

    Hi there, Sorry for my ignorance but been a while since I did stats. I am comparing mortality rates between two breeds of pigs. My ultimate goal is to figure out whether the difference in the rates can be explained by random variation or whether there is a breed effect (assuming all other...
  11. M

    Estimating Mean of a Poisson Distribution Based on Interval censoring

    Dear all, I appreciate that if you let me know if there is any package implemented in R for Estimating Mean of a Poisson Distribution Based on Interval censoring? And if yes, could you please provide some information about it:) By the way, is there anything for lognormal?I think...
  12. N

    Plotting the results of GLM in R

    I have this data plotted as a scatter plot in Excel I had done a regression in Excel, and the p value was 2.14E-05 while the R- value was 0.32. I was told the R value was too low compared to the significance of the p value, and was told to control for the dispersion of the data by running it...
  13. H

    Estimating Failure Rate: Chi-Square v Poisson

    I understand Poisson distribution is for discrete events and can be used to estimate failure rate to a given confidence level from elapsed time and number of failures (assuming constant failure rate). However, in safety system engineering I routinely see the Chi-squared distribution used...
  14. J

    Poisson model on moving averages: non-discrete

    I have a model that is based on counts of cases. It follows a poisson distribution quite well but we are unhappy about the results of the model. In order to improve it we wanted to use moving averages of the counts instead of the counts themselves as the dependent variable, but this changes my...
  15. W

    conditional distribution functions.

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  16. S

    Poisson and binomial distributions

    I composed this question: A hospital has 20 ambulances and on average 2 break down a day. There are five ambulances in reserve and if more then five ambulances break down in a day there are problems. What is the probability that in a 30 day period there will be problems? My approach is this: I...
  17. F

    Process capability - Negative Binomial

    Dear All, I have attribute that show overdispersion and seem to be distributed according to a negative binomial distribution. I have the following questions: 1. How can I check in Minitab if my data is distributed according to Negative Binomial? (I used Crystal Ball for this specific...
  18. R

    Comparing means with Poisson distributed data?

    Hi everyone! How can I perform ANOVA, so to compare means, when the data of my groups are clearly Poisson distributed (towards 0 values)? Thanks a lot! Cheers
  19. N

    Propagation of Poisson Errors

    How do I combine the asymmetrical errors when I subtract my samples from the controls? I know my low counts follow a Poisson distribution and therefor I cannot simply add in quadrature as per Gaussian errors. Thanks in advance, N
  20. noetsi

    Comparing data to a theoretical discrete distribution

    With continuous data you can test if your data meets a theoretical distribution with a QQ plot. However, SAS won't generate these for discrete distributions such as Poisson (with good reason as the author notes in the link below as the results are dubious for such a distribution). The author...